Single “Multiple Inputs Tx” vs Multiple “Single Input Tx”

Question

Alice owns three addresses A1, A2, A3. She decides to collect the coins held by these addresses into a single coin so she generates a fresh new address A4 for that.

She has the following two options:

1. Single transaction

+--------------+ |A1 A4| |A2 -> | |A3 | +--------------+

2. Multiple transactions

+--------------+ |A1 A4| +--------------+

+--------------+ |A2 A4| +--------------+

+--------------+ |A3 A4| +--------------+

---

She does not want people to know that A1, A2 and A3 are owned by her. And she does not intend to use any mixing services. She also don't mind paying more transaction fees as in option 2.

Option 1

A1, A2 and A3 can be linked together assuming she did not use any Coin Join technique.

Option 2

It can be seen that A4 is reused to receive payments. However A4 has never been seen before this transaction.

Questions on Option 2:

1. Can someone observing the Blockchain deterministically figure out A1, A2 and A3 belong to same user?

2. If Alice now spends A4 to Bob (sends all amount, she never uses A4 again), can Bob ever figure out that A1, A2 and A3 belonged to Alice?

3. What privacy will Alice (or someone down the trail, like Bob) lose if she goes for option 2?

4. Is reusing addresses to only receive payments and spending that address only once okay?

Answer 1

1. I don't think so without any extra knowledge.
2. Same as above.
3. Option 2 looks more anonymous because Option 1 shows that A1, A2 and A3 know about each other enough to be able to transact together.
4. That is very common scenario and recommended by many wallets.