Question about PR Renewal and HDB

[punpun711]

My husband and I have got PR since 2007 and have already renewed 1 time (5 Years) under Professional scheme, we have got PR before we got married. Then we have 1 child born in Singapore and he got PR under my sponsor. We have bought HDB for 3 years.
However, one year after PR renewal, my son and I have migrated to Oversea, while my husband is still working in Singapore until now.

My REP will be expired in June 2019, but I’m planning to go back to SG to renew my REP online.

1. Will ICA consider to change my son and my REP to be family scheme (under my husband sponsor)?
2. If we got rejected, how to appeal to ICA.
3. For this case, we are forced to sell our HDB within 6 months, is that correct? Is there any option we can maintain our HDB? What if after 6 months, there is still no buyer?

[PNGMK]

If ICA establish that you and your son and presumably your husband have migrated I don't see why they would renew your REP. Your husband's is at risk as well as yours and your sons. There is no 'standby PR what' now in Singapore. The Indians freak that one up.