Well ....There is no such thing tat if u put some different plugs of different spec ..check engine light will get open....! it wont trigger CEL as there is nothing to CEL with plugs but engine starts to behave bad...!
B/w..Plugs Recommended for Platz from TOYOTA Motor Corp Japan are as follow...
Platz 1.0L(1SZ-FE Engine) uses Denso K16R-U
Platz 1.3L(2NZ-FE Engine) uses Denso K16R-U11
Platz 1.5L(1NZ-FE Engine) uses Denso K16R-U11
2.Yes ..Z-Gen engines uses timing chain instead of belt as it last longer than belt.......!!! but exp....! as per my Info..1.0L engine used in Platz/Vitz timing chain cost 7000/- Rs in market nowdays...! if its really timing chain..do replace it as soon as possible....!but make sure its timing chain...not anything else...!
Get Plug a/c to this this given name above..dont get beside it or your engine starts to behave bad....!