I finally solved all problems. Now 1.7.8.6. works excellent. No need for core.js or other setting outside normal upgrade. From 1.7.7.4 do 1.7.8.6 What I do?
Step 1.: deactivate all modules not made by presta (only default modules are active) prestashop 1.7.7.4
Step 2.: download all updates from 1.7.7.4 to 1.7.8.6 to pc
Step 3.: unpack all zip files in separate folders as update (eg zip of 1.7.7.6 to folder presta 1.7.7.6, etc)
Step 4.: in BO I go to 1-one click upgrade, put my shop in maintenance mode. In this module section "Start your upgrade" go to "expert mode" and choose Channel "Local directory" and in "Please tell us which version you are upgrading to (1.7.0.1 for instance)" wrote first next ugrade above 1.7.7.4.
Step 5.: with Freezilla (or other upload software) I upload folders in his origin unzipped folder to folder /admin/autoupgrade/latest/ . (In my folder presta 1.7.7.6 I copy zip file for this upgrade and than unzipped)
Step 6.: start ugrade.
Step 7.: I refresh the page, log out and login to my presta. And deleted all folders inside /admin/autoupgrade/latest/
Step 8.: repeat steps from Step 4. to step 7. with another ugrade version 1.7.7.7. and so one.
Step 9.: After I finish upgrading final 1.7.8.6 I start activate modules I was deactivated in Step 1, activate one by one and check if it is work. Some modules not worked and deinstall them.
Step 10.: Check translate on my language, made some translating, try to "place an order" as buyer and all works excellent.
So I upgrade one after another till rich 1.7.7.6---1.7.8.2---1.7.8.4---1.7.8.6
After all that, indexed and clear cache.
Hope this will helpfull for all.