Questions about saving data to flash

[kukoldiega]

I am working with an STM32D103C8T6 and I want to store some data on the flash memory.
I have some idea on how to do It but not sure about some details.
My procedure is the following:

1- Add a new section in linker at a defined address near the end.

I understand this is done so main program never overrides my data. If not please correct me
ex:

.permament 0x800EA60 :
{
 KEEP(*(.permament))
}>FLASH

2-  Unlock flash and option bytes with 
FLASH_CR and FLASH_KEYR registers.

3- Clear page inside the area I destined for my permanent data

4- Write my data in 16 bits packages
eg:

*(__IO uint16_t*)(addr) = data;

I have the following questions:
Regarding step 1:
Is this necessary? Does this guarantee I won't overwrite the main program or is it any other way to do it?

Regarding step 2:
Do I need to unlock option bytes or is this ?

Regarding step 3:

Where does a page start? Do I need to specify the addres in FLAS_AR register to the begining of a page?

Regarding step 4:
I know I cannot write 1s but can I write ceros anytime?
For example, can I do the following?:
  Let's say I have 4 bytes with all 1s, I then write in the first byte a 3.
  Some time later I write in the second byte a 5.
  Later I change second first byte to 1.

Can I do this or do I need to clear the page after each write?
 

[kukoldiega · Accepted solution]

I will create a response which answers all the questions based on what I ended up doing:
1) I created a new memory area

MEMORY
{
  RAM    (xrw)    : ORIGIN = 0x20000000,   LENGTH = 20K
  FLASH    (rx)    : ORIGIN = 0x8000000,   LENGTH = 63K
  STORAGE_FLASH (rx) : ORIGIN = ORIGIN(FLASH) + LENGTH(FLASH), LENGTH = 1K
}

 and assigned a new section inside it for memory initialization:

  .permanent :
  {
    . = ALIGN(4);
    KEEP(*(.permanent))
    . = ALIGN(4);
  } >STORAGE_FLASH

 And I created a new symbol to track where to write:

  __flashStorageBegin = ORIGIN(STORAGE_FLASH);

 2) No need to unlock option bytes

3) Page start is aligned with "FLASH" area, since page is 1kB long for this MCU, all pages are a multiple of 1024 bytes from  FLASH origin (0x8000000+1024*n)
In the FLASH_AR register you should only write a page start address.

4)You can write the same half-word multilple times without erasing the page mulitple time as long as you don't write 1s.

Extra information from other question I did: 
Since you have to write to half-words, you should only write to even addresses.