An interesting question. I think it largely depends on what we mean by 'the daily grind of modern life'. If the assumption is that modern life is associated with a lack of opportunity at the workplace to be creative, or the lack of time to pursue creative interests, and so on, then it is clear that one's motivation to be creative will be negatively impacted under such conditions.

The question though is whether modern life is associated with more of an onerous daily grind than pre-modern life? After all, modern life comes with many advantages - virtually instantaneous access to knowledge and creative stimulation, more opportunities for creative exploration and expression (e.g., even without gatekeepers - blogs/self-publishing), etc.

Perhaps the case may also be made for the opposite - that the endless opportunities for ready distraction and varied entertainment in modern times means that it is easier to spend our leisure time in passive forms of interest engagement, rather than the active engagement required for creative pursuits.

Anyone can improve their creative ability if they have the will, perseverance and dedication to do so. Start by defining the area in which you'd like to be more creative (e.g., a literary domain like poetry writing). Then cultivate and hone your practice around what you are trying to achieve. In time you will develop a keen understanding of the workings of your creative process which will be unique to each individual (e.g., for many, a walk helps when facing a impasse while others may prefer another strategy, like playing a game of chess). To take a simple analogy - approach it in the same manner as you would in going to the gym to achieve a desired level of fitness. Identify your aims, put in the work, and stick with it.

Yes, it is skill than can be developed with practice.

The evidence so far in relation to this question is inconclusive. It is also worth keeping in mind that preferential use of a limb or an appendage on one side of the body is widely found in many other animal species, and is not exclusive to humans (see https://doi.org/10.1371/journal.pbio.1001767).

No, you are not less likely to be creative. In fact, creativity is inherent to the process of discovery in the fields of mathematics and science as well.

The short answer is 'yes'. Although there is no dearth of anecdotal evidence to support the link between intuition and creativity, it has not been directly studied much in empirical work owing to the difficulties associated with the evaluation of these process in real time (see https://www.frontiersin.org/articles/10.3389/fpsyg.2016.01420/full).

In many different ways depending on the type of creative pursuit in question. Here is an example for the visual artistic domain of behavioral and brain changes following an 11-week art course: http://www.alexschlegel.com/research/

Some people clearly exhibit extremely high levels of proficiency in creativity-relevant skills at a very young age. Mozart is a prime example. However, this is not true of the vast majority of people who go on to become recognized for their creative talent and generativity.

No, not so far directly in my own work.

No. There is actually little evidence to suggest that creativity declines with age. People go through lower and higher creative periods of course. And the demands of everyday life can mean that your capacity to be creative may be not be actively engaged for a long time. But the creative capacity when unengaged is best viewed as 'dormant' rather than 'lost'. The fact is that our capacity to be creative is remarkable resistant to degeneration - which is why it is often targeted in the context of rehabilitation for conditions that are marked by cognitive decline (e.g., dementia).

Creativity refers to our ability to generate ideas that are novel and fitting in a given context. There is general consensus on the basic elements of the definition, but where the differences emerge are at the level of how creativity is operationalized and investigated. See this paper for an overview of the theoretical background: https://www.researchgate.net/publication/254301596_The_Standard_Definition_of_Creativity

Several networks of brain regions and neurotransmitter systems are involved in tandem in creativity. For a gist or general overview of the picture, please read the following Scientific American Q & A: https://blogs.scientificamerican.com/beautiful-minds/the-neuroscience-of-creativity-a-q-a-with-anna-abraham/

Yes, domain-specific expertise is essential in order to be creative in a particular field. The question that remains is how much expertise is needed.

The 'foundation' view suggests the relationship is linear, i.e. that the more expertise a person has in a domain, the higher the likelihood of creativity exhibited by that person in that domain. The 'tension' view suggests the relationship is an inverted-U, namely that too little expertise (due to lack of essential knowledge) or too much expertise (due to the tendency to be blinkered or constrained by existing knowledge) is not conducive to creativity.

There are several resources that are freely available online to the general public (e.g., parenting magazines) that provide carers tips for encouraging the creative imagination of their children. These may be useful to peruse to get a sense of what would work best for your unique context.

Some academic resources (PDFs can be downloaded at the provided URL) that you may find interesting:

1. Zeynep Dere - Investigating the Creativity of Children in Early Childhood Education Institutions: https://eric.ed.gov/?id=EJ1207637
2. Małgorzata Wolska-Długosz: Stimulating the development of creativity and passion in children and teenagers in family and school environment - inhibitors and opportunities to overcome them: https://www.researchgate.net/publication/277651296_Stimulating_the_Development_of_Creativity_and_Passion_in_Children_and_Teenagers_in_Family_and_School_Environment_-_Inhibitors_and_Opportunities_to_Overcome_them
3. E. Paul Torrance: Is Creativity Teachable? https://eric.ed.gov/?id=ED120651