Can you reclass to jobs in the Army that require you to get a top secret clearance if you only have a secret clearance?

No, you'll need an interim to request training for the MOS you want. Expect a nine month (ish) wait till you get your interim TS. You'll need a fully adjudicated clearance to hold the MOS. Your career counselor can help you submit your request

I did. Super easy.

Yes you can, one the requirements during the reclass process will be to upgrade your clearance.

For instance if you reenlist for said MOS, then you'll get the orders which will be used as the "reason" to upgrade, then depending on the MOS AIT you may be able to go through with an interim.

I can add some personal experience here.
I am prior-service RA 11B.
I joined the NG last year as a 35F and am currently waiting the TS to wrap up.
So, as mentioned before, you CAN reenlist into an MOS that requires a TS clearance but you'll at least need an interim before you can be exposed to TS material (AIT).

No.