We can couple the auxiliary verbs ser/estar with a past participle, and we can conjugate ser/estar in the perfect past or imperfect past, so in total we have four combinations in past tenses. Take the past participle of the verb “abrir” as example:
1. foi aberto
2. era aberto
3. esteve aberto
4. estava aberto
Do all of the four combinations occur in european portuguese? And what are the differences in their meanings? Can you give some example sentences to illustrate when to use them respectively in context?