install front sensor from outside void warranty or not? installer said plug and play only

i am planning to buy second car. not really for long distance as have another SUV. for city driving only with average of 3 days per week of using. Is it okay just to consider the basic honda city without hill assist, vehicle stability etc

do you need this injector cleaner or fuel additive in service? when i refuse saying that normally use for old car, and then silly remaks by the CS ya.."dah teruk baru guna". hahaha then i said oh honda engine oil no good is it that you need more additive?