voraa,
а без flex-direction: row-reverse; сможешь?
<!doctype html>
<html lang="ru">
<head>
<meta charset="utf-8">
<title>index</title>
<meta name="viewport" content="width=device-width,initial-scale=1">
<meta name="description" content="index">
<meta name="Keywords" content="index">
<style>
.blok{
width: 600px;
height: 100px;
margin: 10px auto;
display: flex;
justify-content: space-around;
/*flex-direction: row-reverse;*/
}
.kvadrat{
width: 100px;
height: 100px;
border: 3px solid #000;
}
.kvadrat.aktiv{
border: 3px solid #0504aa;
}
.kvadrat:focus{
outline: none;
}
.blok .kvadrat:hover~h1{
color:#0504aa;
}
</style>
</head>
<body>
<div class="blok">
<button class="kvadrat aktiv">1</button>
<button class="kvadrat">2</button>
<button class="kvadrat">3</button>
<h1 class="zagolovok">Заголовок</h1>
</div>
<div class="blok">
<button class="kvadrat aktiv">1</button>
<button class="kvadrat">2</button>
<button class="kvadrat">3</button>
<h1 class="zagolovok">Заголовок</h1>
</div>
<div class="blok">
<button class="kvadrat aktiv">1</button>
<button class="kvadrat">2</button>
<button class="kvadrat">3</button>
<h1 class="zagolovok">Заголовок</h1>
</div>
</body>
</html>