when we speak about specific transaction: no. The unconfirmed transaction looks exactly the same as the same transaction with 1,2.. confirmations.
yes. There are 3 types of transaction: confirmed, unconfirmed, and nonexistent
example of nonexistent are those 10BTC I'll give you tomorrow.
difference between unconfirmed and nonexistent is not "obvious"
When you see an Unconfirmed tx on your PC, this does not "guarantee" that everybody else sees it too. If internet connectivity fails, you may be precisely the only person who sees it.
Unconfirmed transactions can be very different from confirmed, in many ways:
Unconfirmed transaction can spend funds that already have been spend, or funds that never existed.
Unconfirmed transaction get lost in the Internet (never get confirmed).
Unconfirmed transaction can be reversed and be replaced by different Unconfirmed transaction sending the funds to somebody else.
Unconfirmed transaction can contain technical error that prevent it to be confirmed.
Unconfirmed transaction can have low fee (less than dust limit) and this can cause confirmation delay of 12 or more hours.
Unconfirmed transaction can be one of many abusive (spam) transaction (in an attack). Such Unconfirmed transactions will typically never get confirmed and most likely all miners will delete these abusive transactions.
Unconfirmed transaction can be censored by all miners. This can happen if some address belongs to a person who is anti-bitcoin or some large corporation that has a conflict of interest with bitcoin (like a large bank). If all miners agree that they do not wish such entity to transact on bitcoin, they may decide to censor the activity of such an entity or person. This transaction may never get confirmed.