2 - There a few UNFINISHED DIY projects based on ICL7135 also
Experienced electronic hobbyists do not waste time and resources building stuff they can buy. Also you need tools you can rely-on. You shall not be thinking which does not operate correctly - thing you are now building or your DIY "measurement equipment".
Some beginners think that they can get cheaper DMM by building it, then they realize that either it is way too limited beyond usability, does not work at all or is way more expensive than one you can buy. That's how many "homebrew test equipment" projects are dropped.