To avoid later disappointment I vote for manual partitioning.

Cook recipe:
Select your HD (sda) with the cursor and apply a GPT partition table. I think the installer does that automagically on efi installs.
Select the free space and add 1024M as new partition, use as EFI system partition.
Select the remaining free space and add 8192M, use as swap.
Select the remaining free space and add 32738M, use as ext4, mount point /
Select the remaining free space and add the rest, use as ext4, mount point /home

Good luck.

If the #11 dialog in your case includes sdb, you need to choose the "No" option to go back to the partitioner and undo any partitioning of sdb that you have chosen.

I tried expert install and it too shows both sda and sdb on the partitioning page and there is no way to deselect sdb (installation usb)

You will always be shown all detected devices, including the installation stick. That does not mean they are all used.

As I said, I don't trust any of the automatisms. You should use manual partitioning, normal or expert mode does not matter. Is that an efi PC or do you want a legacy installation? Encrypted or standard? How much RAM is available?

How to edit topic?

Refer to my previous post #9.

I guess you are using Guided Partitioning. Have you got sufficient free space on your sda drive? Is this a dual boot possibly?

It would make sense if you would be a bit more responsive and open with the information you are disclosing here.

Please open above link and see the image after point no. 11.It only shows sda but in my pc it shows sda (hdd) and sdb (installation usb). Even though i only select sda.

What the release is concerned, do you want to use Daedalus, or Excalibur (Testing) or Chimaera or anything older?

I am not aware about some "official" guide for manual partitioning. On the Devuan website there are installation guides with screenshots, but they use guided partitioning there. You might look at Debian, if they have some document. Or search for a video on YT. It does not matter if Devuan or Debian, the procedure is the same, and the chance to find something or Debian is much higher.

Well, lets start with determining what we are talking about. There are five or six netinstalls around. Which release do you talk about? Where did you get the iso from?
Then: standard installation or expert install?
Guided partitioning or manual partitioning?

I've been through some installs with Daedalus netinstall recently, no problems in expert mode with manual partitioning. I dislike using any automatism, they all have their limitations and disadvantages.