1. The use of the indefinite article implies that more than one shop are involved. On second thought, I'm trying to envisage a conversation with "it's a little shop of my own"...
Perhaps it could be used even if you have only one. People don't always go by the book (= the grammar book
) when they speak and write.
For example, it says in all grammar books that the combination the ... + of one's own is wrong. In other words, we shouldn't say: This is the car of my own. Yet an English pop singer called Cliff Richard sold a million records (or more, I don't know) singing:
And some day when the years have flown
darling, then we'll teach the young ones of our own.
- The Young Ones
2. You can say from Monday to/till/until Friday. Since instead of from is wrong simply because native speakers don't use it with to/till/until. It has nothing to do with tense. There is no verb in your original example.
CB