My first time to SIN will be a 115m layover HKT-SIN-DPS all on SQ. How realistic is it to squeeze in a quick visit to Jewel?

My understanding of protocol and speed enhancing features:

1. Log arrival info into MyICA app 2-3 days before.
2. Request stamped paper BP SIN-DPS in HKT.
3. Clear immigration & customs.
4. SkyTrain T2-T1, then walk to Jewel.
5. Same way back to T2 after visiting Jewel.
6. Scan BP at turnstile followed by security screening.
7. Proceed to gate.

Any FastTrack immigration/security for *G flying J?

Will SQ board a 787-10 50 min prior to departure?

If time allows, is SQ Business Lounge best in T2? I’m *G flying J.