2D Isometric Game Questions

I'm creating a 2d isometric game and I need help changing the way my character moves. I have a few questions:

I would like for the character to have no acceleration and deceleration when moving (start moving at max speed right away and stop moving right away)

How can I make my player face left / right / up when idle? It's set to facing down when Idle so when i move up and stop moving, it faces down when idle and i don't really like that.

Also I'd like to know how to do this with Attack animations as well

Here is my current script:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;

 public class PlayerController : MonoBehaviour {

 public int Speed = 1;
 [Tooltip("How much damage we deliver on a hit to others")]
 public int HitStrength = 10;

 private Animator _animator;
 private Rigidbody2D _rigidBody;
 private SpriteRenderer _spriteRenderer;
 private GameController _gameController;

 private float _horizontal;
 private float _vertical;
 void Start()
 {
     _animator = GetComponent<Animator>();
     _rigidBody = GetComponent<Rigidbody2D>();
     _spriteRenderer = GetComponent<SpriteRenderer>();
     _gameController = GameObject.FindGameObjectWithTag("GameController").GetComponent<GameController>();
 }
 void Update()
 {
     _horizontal = Input.GetAxis("Horizontal");
     _vertical = Input.GetAxis("Vertical");
     _animator.SetBool("WalkDown", _vertical < 0);
     _animator.SetBool("WalkUp", _vertical > 0);
     _animator.SetBool("WalkRight", _horizontal > 0);
     _animator.SetBool("WalkLeft", _horizontal < 0);
     
 }
 void FixedUpdate()
 {
     _rigidBody.velocity = new Vector2(_horizontal * Speed, _vertical * Speed);
 }

}