whenever i  load the page , the option is automatically selects the last
value of the picklist. <option Selected> is not working.
how can i make the particular option value to Selected? 
pls help me on this.

HTML
<select size="1" name="Country Name" onchange={changeHandler}>
              <template for:each={CountryList} for:item="country">
   <option  selected={selectedCountry} key={country.key} value={country.Id}> 
      {country.Name}</option>
              </template>
  </select>
---------------------------------------------------------------------------------------------------------
js
 @track selectedCountry=false;
 @api countryId='';
 connectedCallback() {
 getCountry({
        recordId: this.countryId,
    })
.then(result => {
      this.CountryList= result;
      if(this.countryId){
        Object.entries(this.CountryList).forEach(
          ([key]) => {
            if(this.countryId === this.CountryList[key].Id){
              this.selectedCountry = true;
}
}

 

after selecting a picklist value for three times, how to disable it ?
example
picklist value for selection__C  are 
1
2
3
if the picklist value "1" should be  picked and saved only for 3 record. for the 4th record it should be at disabled

Picklist field- Type_Of_Bedroom__c
its values are 1bhk(30 unit),2bhk (30 unit),3bhk (20 unit)
if a user select 1bhk and if he saves the record, the picklist value should be changed as 1bhk(29 unit) is that possible ?

how to make a number  field(total units__c) as a read only, non editable and that field should have default value. for example , if (total units__c) is set to a default value 10.whenever a status__c(picklist) is selected as sold,the (total units__c) should decrease by 1

hi, I am newbie to salesforce. I am about to create a sample as like as dream house app but with small changes.by only using process builder and validation rule, relationship. Scenario is xyz company has two vendors for their apartment construction. And here enquiry is made by the customer and if the enquiry is won, it should be converted as like as lead object, but instead of opportunity here it is converted into custom object(booking). Company has to track, which sales person from the sales team is dealing with the customers and Needs to check status of the construction from vendor. How many objects are possible here? As per my idea, I created 4 object-enquiry (acts a lead), booking (enquiry is won, booking is created), sales team (relation with vendor, booking, enquiry), vendor is my idea is right?
 

how to make a number  field(total units__c) as a read only, non editable and that field should have default value. for example , if (total units__c) is set to a default value 10.whenever a status__c(picklist) is selected as sold,the (total units__c) should decrease by 1