If the keyboard is hidden, there doesn't seem to be a way to reopen it.
Also, if the app loses focus, then even if they keyboard is open, it doesn't work.
Issue apparent on Nexus 5X.
still don't see full picture how TIC will work on mobile
have two variants, TIC looks like on PC but with custom touch keyboard and you can make a game even on tablet/phone or just like an app to open .tic files and play them with virtual gamepad (not sure that anyone would want to have coding on touch device).
not yet, here is an issue https://github.com/nesbox/tic.computer/issues/60