Updated Problem Statement:
Need help on the syntax for the computing date difference between current time (now) and a pre-set datetime (Need By Date).
Variable: Need By Date (DateTime)
Simplified Trigger. Trigger is working and runs a query every five minutes. Objective is to compute the test hours remaining in every issue.

1. {{now.diff("Need By Date").hours}}
No Errors on the automation but returns a null result.
2. {{(now).diff("Need By Date").hours}}
Error on execution.

3. {{"Need By Date".diff(now).hours}}
Working but negative results.

4. {{"Need By Date".diff(now).hours.multiply(-1)}}
Works perfectly fine.
I need to put an extra process on my computation just to get the desired result.
My question is what would be the correct syntax if i reverse my variables (1 and 2) instead of the (3,4) approach.