1/ I believe that our individual consciousness is always changing in subtle, non-linear ways. So, yes. If you will it to change.

2/ Now you've got me wondering about the intrinsic Problem of Forgetfulness. You could choose to forget, or to modify, a memory. I am forgetful some days, and not others, so my experience so far is too subjective to really know.

3/ Sure, if you're picturing yourself, waking each morning, rebuilt anew, with facets of your multidimensional consciousness working as a team to become a truer version of yourself as you go. You are You

4/ Yes

5/ Look into Astral Projection

6/ and 7/ not in my experience physically, but I've felt subconscious influence from skewed versions of space/time (i.e. worldlines that have ceased to exist, but persist throughout time as worldlines continue to converge).

8/ Pinpointing the exact moment of a shift is like trying to stay conscious when falling asleep. Just let go and let the pieces fall into place

9/ There's no set time, as each time you catch your reflection, you will find yourselves there for a new purpose. I cannot tell you how you should/ will feel, but maybe, try to accomplish your intended goal, and leave with vigor and zeal. You won't know until you know, so don't waste your time and energy trying to confirm that you hold the power to change things.

10/ Sure

Best of luck to you