Hello Symon
Let's say you have two backups taken.
1 - Full online taken on Monday (9:00 AM CET - 11:00 AM CET)
2 - Incremental backup taken on Wednesday (9:00 AM CET - 10:00 AM CET)
On Thursday you want to do a restore to get the data until the end of the Wednesday backup time (10:00 AM CET). In this case you will first need to restore the full backup taken on Monday and then apply the incremental backup taken on Wednesday OR apply the archived logs created from Monday (11:00 AM CET) until Wednesday (10:00 AM CET). Check this link 4.4 RMAN Incremental Backups to understand what the RMAN incremental backup is all about.
Regarding the restore part, yes you will need to restore the control files and put the DB into mount status before you start the restore.
RB