Notes

Requirement: I want my google calenders (only selected ones) to appear in the calender 5 app

Settings: I have my own calendars which I work with plus around 10 other calenders in my google account which are shared by my colleagues with me (to allow me to see their schedules). I usually don't want my google-web-calendar view (at https://www.google.com/calendar/render) filled up with all other's events therefore I switch them off in my browser view (just by clicking on any calender toggles it on-off). This means that these shared calendars are set to "show in the list" in Calendar Settings on the Google calendar website.

Local iPhone app works fine:
1. Using Safari browser on my iPhone i visit https://www.google.com/calendar/iphoneselect and select ALL calendars to be synced with iPhone app (my own + shared)
2. In the iPhone calendar app, I have "Calendars" option (bottom middle) which can be used to select the calendars to be shown in the app. Non-selected just don't show up. simple. It works.

Calendar 5 app:
I tried everything but nothing works good.

Try 1: Don't use google account at all. Just use local calendars option
In option -> Connect to Google Calender : NO
In option -> Local Calendars : local calendars is checked, Google Calendars is unchecked (to avoid duplicates)
Result: Shows calendar events even from calendars which are unchecked in local iPhone app. iPhone app does not show those events. Don't know from where calendar 5 app is picking them (when google account is not connected).

Try 2: Connect google calendar
In option -> Connect to Google Calender : YES
In option -> Local Calendars : both options are unchecked (to avoid duplicates)
Result: Again shows all events. Why I cannot select individual calendars when app has access to my calendars?
A bad Fix: I changed my Google calendar setting on web. and unchecked "show in the list" for my shared calendars. Now calendar 5 app does not show useless calender events. In my iPhone app, I still has option of selecting or deselecting any calendar (great). BUT on my google calendar webpage (https://www.google.com/calendar/render), I cannot see the list of those calendars which means that I cannot toggle on/off a calendar when needed. (THIS IS BAD and cannot be compromised)