I wish · If only · Would rather
Use past simple after 'wish' to talk about an unreal present — something you want but don't have. 'Was' and 'were' are both acceptable; 'were' is more formal.
Use past perfect after 'wish' for past regret — something you didn't do (but wish you had) or something that happened (but you wish hadn't).
Use 'wish + would' to complain about someone's annoying behaviour. Can also be used with things: "I wish it would stop raining."
'If only' works exactly like 'wish' but expresses stronger emotion — regret, frustration, longing. Often used with an exclamation mark.
Different subject → past tense. Same subject → infinitive ("I'd rather stay home").