I have a cake that I'm doing for delivery on December 17th. I would like to do all the elements way in advance but wondering what is the best way to handle each listed at the bottom?

A few questions for separate elements being made:
a.) How far in advance can I make them?
b.) Best way to store them so they are flexible

I'm making a studded belt look around the bottom as a border. It needs to remain flexible without cracking etc.
a.)?
b.)?

Elements to be dusted or painted onto fondant
a.) How far in advance can I paint them?
b.)?

Duplicating a clients tattoo to be put on the cake. Needs to remain flexible.
a.)?
b.)?

Numbers and Letters
a.)?
b.)?

Also I'm making a molded muscular arm out of RK
a.)?
b.)? - however not FLEXIBLE

ANYONE? Please help with this. I would like to start today on some of these if it is reasonable to do so. Thank you

If I make things that need to remain flexible, I store them in an airtight container. If you are painting on the fondant, it needs to dry and it wont if you stick it in an airtight container, you can doo all of this as far away from the date as possible, I think diluting the color with vodka helps it dry quicker so you can get it in an airtight container quicker. Make the RKT arm a few days ahead of time (or longer), then let it sit out so it firms up. I suggest on the belt, you make that right before you add it to the cake to prevent cracking ( I dont know if its going all around the cake) then just take a little tylose or gumpaste glue and stick the studs on. I had all the elements of my highschool reunion cake (in my pics) done 3 weeks before I put the cake together, used a tupperware sheet cake container to store them in because its long and has an airtight lid.

.....molded muscular arm out of RK; not FLEXIBLE.....
I would think this can be started- probably completed - now

........Elements to be dusted or painted onto fondant a.) How far in advance can I paint them? ...
From my experience you probably can start these now.

For most decorations that needs to remain flexible you can cover/wrap well w/saran wrap and freeze or at least keep in frig.

How do you plan on doing the tatoo? Is it going to be like a plaque? You could make a fondant plaque and pipe the design on it, then wrap and fz. I haven't done it but yuou might be able to pain on fondant rather than pipe.
Try a sample - take a small piece of fondant and paint (w/food color) and also pipe another & fz to see how it comes out after a few days.

I would try painting on a scrap piece of fondant and put it in the fridge, then take it out and make sure it doesnt run with the condensation that forms on it when it comes to room temp. The condensation evaporates and the fondant is fine, I dont know if the painting will run or not. Kakeladi probably has more experience with this than I though.