Seems my app hasn't saved my new development

hello guys I’ve been building my app slowly for months now and I had some major progress lately

I had returned to my app and now seems to not have saved my previous development

is there any advice you can give to help with checkpoints along the way as to how to avoid thing like this

for example would I be better purchasing a monthly while I build so that I get some extra features

would there be obvious tips that I could refer to…

any help would be great…