Screwing telephonic interviews.Am I too much underprepared for FANG?

I have been actively giving interviews for last 1 month but fucking up telephonic (70percent) round even after solving and revising 200+ LC questions.
But not losing confidence at all.

Am I underprepared for Google/Netflix/Apple/ Facebook. My deadline for switching is October end.
Below is my fucked up story in chronological order:

Houzz: lc medium, wrote buggy code.

Zume: 2 questions, lc easy(completed) and then lc hard extension(partial) both in 40 mins.

Nutanix: leetcode simple, screwed because of interviewer inexperience. went into different directions to solve problem. All test case passed which was given in original question. He introduced 2 more test cases that also passed the. He gave 2 more which broke and 40 mins passed.

Oracle: 1 hr telephonic , how to sort a file which 10 times larger than memory. Non -coding. I gave semi-cooked explanation using merge sort.

Amazon: find size of a given folder in a computer directory structure: coded in sloppy way using n array tree. Worked fine. Asked for optimization, I applied dp which was not necessary i think.

C3iot:used a generic concept when asked for a bst specific question. The time complexity was same for both approach. why the interviewer was so much into bst way. He could have told me earlier that he only want the bst way.

VMware: did not have very firm grasp at mutithreading when interviewed. First company grill on all things like web api/db/ssl/http than algo.

I have some onsite though in small companies. Let see what happens.

Yeo: 5 yrs in total(1.5 yeo post MS)
Current Tc==base== 130k
Target:170k base /200K tc
location : bay area