Peak load upgrade and downgrade SQL Server 2017 Standard  SQL Server 2017 Enterprise
Answers to your questions below, this doesn´t necessarily mean that I think it is a good idea, it seems quite a high risk approach to me.

Yes restoring a standard edition db to enterprise edition just works as long as it is not on a later version than the destination server.
Restoring an enterprise edition to a standard edition works AS LONG AS you have not started to use enterprise features

you can query sys.dm_db_persisted_sku_features
see
https://www.brentozar.com/blitz/enterprise-edition-features/