Questions in DONTFORGET

Hey, do I still need to log in on a PC before I can log in on mobile

I had Froggit outside Toriel's house but after killing one due to how bad it was in level that Froggit disappeared and now comes out as lost, is there any way to get it back or if I choose to gain experience I lose any chance of having those monsters?

I dont understand like i want to be a pacifist in the game but if i do that i will not be able to gaine level and get accse to chest and if i attack enemy i will not be able to be freind with them what do i do

Can there PLEASE be a way to resize the buttons on the mobile version? Thank you!