Can main pass holder (Employment or S Pass) apply for LTVP before the main pass (Employment or S Pass) application is approved?

Is LTVP allowed to be applied before approval of main pass (Employment or S Pass) application?

Yes, you can.

However, MOM recommendation is to wait until after the main pass is approved. If the main pass application is rejected, your Long Term Visit Pass (LTVP) will also be rejected, and your application fee will not be refunded.