** writing multiple block on same element is right approach in BEM ? *
<div class="block-1 block-2 block-1_modifier block-2_modifier">
<div class="block-1__element1">
<div class="block-1__element3 block-2__element2">
</div>
</div>
<div class="block-1__element2">
<div class="block-1__element4">
</div>
</div>
</div>
Yes, this is partially correct, although your naming convention above should be more like:
See corrections: