If one has enough cash to settle a few loans, usually he/she doesnt have to do this kind of trick, just straight away apply 3 loan saja.

Strongly agree to skip this idea.

3 scenarios to be happen. ( say each condo RM 500k )
Apply 3 banks for RM 450k each and accept all the banks for 3 different units

1) Loan executed and money disbursed. Nothing happen.

2) One of the bank catch you ( checked your CCRIS ) during execution or before disbursement. Therefore, if your name only has these 3 HLs, then according to LO, you're suppose only eligible to get max 70%, therefore, loan reduce to 70%. If you have 1 HL now, buy 3 x 500k condo and apply 3 banks to act as 2nd HL, then 2 units have to reduce to max 70%

3) Most critical. Whether you only has 1 HL or no. Or only 1 or 2 units of the 3 loans you accepted. The banks will cancel the facility and reconsider your application and treat it as fresh application. What is each bank take 3 HLs commitment together and your income is not eligible to grant a loan approval. Same goes to other banks in this scenario.

What happen if all 3 banks loan cancel by banks and you had paid 10% deposit and S&P all signed?

I leave it to you for this.